1. Field of the Invention
This invention relates to a straightener roll machine for straightening the deformation of the rim of a brake shoe resulting from soldering a web to the rim of the brake shoe. More specifically, it relates to straightening the distortion of the rim and the twist thereof against the web.
2. Background Art
As shown in FIG. 5, a brake shoe is fabricated by welding the circular end face of a web 21 to the inner peripheral face of a rim 20. However, the rim 20 is prepared from a steel sheet and consequently the inner peripheral face of the rim 20 is barely secured to the side of the web 21 at a right angle. Moreover, the problem is that the circular face of the rim 20 may be distorted when both of them are welded together. In other words, the deformation, if any, of the rim 20 must be straightened.
Press machines and dies had once been used for straightening brake shoes but a roll system is now instead in use. The change in the use of machines and dies requires not only a greater percentage of floor area and space occupied but also increases the cost of equipment. Machines and dies also worsen the work environment due to the generation of noise and vibration.
The conventional roll system is characterized by the steps of fitting the web 21 of a brake shoe into a groove bored in a main roll, mating the under surface of a rim 20 with the surface of the main roll and sandwiching the rim 20 under pressure between the main roll and a dependent roll. More specifically, the main roll shaft is supported by a bearing fixed to a frame, whereas the dependent roll is supported by a bearing whose position is adjustable in the longitudinal direction relative to the frame so as to make adjustable the space between the main and dependent rolls according to the thickness of the rim 20.
The conventional roll system thus constructed allows the application of counterforce to the dependent roll at the time of straightening the brake shoe, thus failing to keep the dependent roll shaft parallel to the main roll shaft because of the movement of the bearing. For this reason, the uniform sizing of one and the other ends of the rim 20 becomes impossible and a great deal of skill not only has been required but also trouble occurs in order to adjust the dependent roll shaft and the main roll shaft to be in parallel with each other.
Moreover, it is certainly too troublesome to make fine adjustments as to the distance between the shafts of the main and dependent rolls in accordance with a subtle changing of the thickness of the rim 20. Furthermore, because the distance between the two rolls is left unadjusted within the range of roughly .+-.9% fluctuations in the thickness of the rim 20, the thickness of the rim 20 has affected finished products in such a manner as to cause differences in their quality.